While the S500 Plug-In Hybrid will be officially revealed at this year's Frankfurt Auto Show, Mercedes announced details -- and showed a few pictures -- ahead of the sedan's auto show launch. The details include engine specs, along with performance data and range.

Of course, most hybrid-car shoppers will be interested in the sedan's engine details. Under the S500 Plug-In Hybrid's hood is a gasoline-powered 3.0-liter turbocharged V6 that makes 328 horsepower and 354 lb-ft of torque. That makes it considerably less powerful than the base-level S550, which offers 449 hp.

Unlike the S550, however, the S500 Plug-In Hybrid also offers an electric motor. That powerplant provides 107 hp and 250 lb-ft, giving the car a lot of muscle. That's proven with the S500 Plug-In Hybrid's 0-to-60 miles per hour time, which is an impressive 5.5 seconds -- less than a second behind the gas-powered S550.

In terms of range, the S500 Plug-In Hybrid is less impressive. In E-Mode, which only uses the electric motor, the S500 can travel up to 18 miles before the gas engine kicks in. While that figure will certainly be enough for many commuters, it hardly compares to the Tesla Model S -- a major luxury sedan rival that can reach up to 310 miles on a single charge. Of course, unlike the Tesla, the S500's gas engine will kick in when the electric motor runs out of juice.

Mercedes-Benz has not yet announced pricing information or a projected release date for the S500 Plug-In Hybrid. But we expect to see the sedan in showrooms early next year, priced well above a standard S550.

What it means to you: The Mercedes-Benz S500 Plug-In Hybrid gives buyers another option in the growing world of electric luxury sedans.

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